The present invention relates to vehicles having fluid reservoirs open to the atmosphere such as an hydraulic oil tank and to the air breather structure that permits air to enter and exit the tank as fluid rises and falls or shifts during operation of the vehicle.
Vehicles having hydraulic cylinders and other devices actuated by hydraulic oil have reservoirs or tanks to store and be a source of fluid as the cylinders and other devices are operated.
These tanks are provided with vents to maintain atmospheric pressure in the tank as the oil levels change. Since the vents are open to the atmosphere, there has to be provision for retaining oil as well as airborne oil particles in the tank while permitting air to enter and exit the tank as oil levels change.
To retain the oil within the tank, two basic approaches have been utilized. The first provides for a long tube to be attached to the tank for venting air into and out of the tank. The very length of the tube minimizes the amount of oil that is splashed up the tube. These tubes are further provided with breather caps at their upper end to prevent oil or airborne oil particles from passing out the vent of the cap. Since the caps are equipped with filtering elements such as foam that serve to retard movement of airborne oil particles out the cap, the cap with its filtering element must be frequently replaced. Further, the very length of the tubes increases part costs and the space they require presents engine compartment design problems.
A second approach used to retain oil and airborne oil particles within the tank as the levels change utilizes a short tube connected to the tank with a splash plate provided within the tube. The plate blocks a major portion of the tube but is configured to permit air to flow around or through it. While this configuration serves to reduce the amount of oil reaching the filtering element in the cap, reduces the frequency at which the filtering element and cap have to be serviced and/or replaced, reduces the cost of a long tube and overcomes its inherent design constraints, it too requires several expensive parts. Further, it also permits an undesirable amount of oil to pass the splash plate, thereby requiring a higher than desirable rate of servicing of the replaceable cap and filtering element.
An additional disadvantage associated with the second design is that it has been attached to the tanks by a threaded connection. Because a great number of tanks today are produced through a rotomolding process to provide a configuration compatible with engine compartment space constraints, any threads formed in the tank are soft. With the threaded splash guard parts that are attachable to the tank being made of harder materials, the threads within the tank can easily be ruined when the splash guard structure is removed and/or installed, thereby requiring replacement of the tank itself.
Accordingly, it would be desirable to provide a splash guard structure for an oil breather and a hydraulic reservoir tank that is compact, reasonably inexpensive and does not unduly interfere with the placement of other components in the engine compartment. It would also be desirable to provide a splash guard structure that has improved effectiveness in retarding movement of oil and airborne oil particles through and out of the breather. It would further be desirable to provide a splash guard structure that can be used with the softer plastic common in rotomolded tanks.
Towards these ends, there is provided a splash guard structure for a rotomolded tank that includes a two stage splash guard arrangement. A first splash guard is provided within a neck portion formed as part of the tank. A bowl-like cavity is formed in the neck portion with a surrounding ring-like chamber that serves as the first stage splash guard. An orifice is provided in the lower portion of the bowl to allow for the flow of air through the neck portion and into and out of the tank as the fluid in the tank shifts or rises and falls. A shelf is formed within the bowl to receive a second stage splash guard plate. A hollow adapter is then threadably secured within the neck portion to secure the second stage splash plate in place on the shelf and an air breather cap with the filtering element is threadably secured to the adapter.
With the first and second stage splash guards, fewer airborne oil particles can pass to the filtering element in the cap and less service is thereby required. Securing the cap to the adapter avoids the repeated threading of a harder plastic part into and out of the soft tank threads, thereby increasing the life of the tank.